Gliederung

Persons with intellectual disabilities are at increased risk for hearing impairment. If left untreated such hearing impairments may aggravate the social and communicative problems of these persons. The aims of this study are to determine the prevalence of hearing impairment and to distinguish between peripheral and central part of detected hearing disorders in this population.

During the German Special Olympics Summer Games 2006, 552 athletes with intellectual disabilities received a hearing screening which included otoscopy, measurement of otoacoustic emissions, and optionally tympanometry and pure tone audiometry (PTA) at 2 and 4 kHz. 20 athletes completed a test battery of discrimination thresholds for frequencies, tone amplitude modulation, and tone duration with both interaural and dichotic protocols.

Of the 524 athletes who finished the screening, 76% passed and 24% failed it. 42% of the athletes were recommended to consult an otolaryngologist or an acoustician. Of the 99 athletes whose screening-based suspicion of a hearing loss was confirmed with a diagnostic PTA, 74 had a so far unrecognized hearing loss. All 20 athletes who received tests for central auditory processing had higher than normal thresholds for tone duration, 15 for amplitude modulation, and 14 of 19 for frequency discrimination in the dichotic protocol reflecting a considerable proportion of central auditory processing disorders in this population.

The prevalence of hearing impairment and the proportion of undetected hearing impairments is high in this population. Therefore, special attention of professionals as well as regular hearing assessment and standard therapy programs are required for persons with intellectual disabilities.

Introduction

Persons with intellectual disabilities are at increased risk for hearing impairment. If left untreated such hearing impairments may aggravate the social and communicative problems of these persons. The aims of this study was to determine the prevalence of hearing impairment and to distinguish between peripheral and central origin of detected hearing disorders in this population.

During the German Special Olympics Summer Games 2006, 552 athletes with intellectual disabilities received a screening of their peripheral hearing abilities and 40 athletes additionally underwent an examination of central auditory processing functions.

Material and Method

Of the 2700 intellectually disabled athletes who participated in the German Special Olympics Summer Games 2006, 552 athletes (214 female, 338 male; age 10 to 69 years, mean 27 years) underwent a hearing screening. The screening was performed at six stations: (1) check-in, (2) otoscopy and ear microscopy, and – if necessary – ear wax removal, (3) evoked otoacoustic emissions screening by measuring DPOAE bilaterally at 2, 3, 4, and 5 kHz, (4) tympanometry screening, (5) pure tone audiometry(PTA) screening, and (6) check-out. Additionally, there were a diagnostic hearing threshold PTA station and a station for testing of central auditory processing functions. Station 2 was failed if there was blocking ear wax which was irremovable, or if anomalies of the outer or middle ear were found. The screening was finished if stations 2 and 3 were finished with a Pass. For those who had failed any of these stations, a tympanometry screening and a PTA screening at 2 and 4 kHz at 25 dB HL were added. Pass and fail criteria of the hearing screening are described in detail in Neumann et al. [Ref.Â 1]. A written recommendation to consult an otolaryngologist was handed out to those athletes who had failed the screening or their caregivers. To quantify the quality of the screening, PTA results were compared with those of a diagnostic PTA at 0.5, 1, 1.5, 2, 3, 4, and 6 kHz. Thus, 101 athletes who had failed the screening, and an additional 94 athletes who had passed the screening PTA, performed a diagnostic PTA.

Because in persons with intellectual disabilities, 40 athletes underwent a test battery of discrimination thresholds of tone duration and sinusoidal amplitude modulation frequency (processing of temporal information) as well as of frequencies discrimination thresholds (processing of frequency information) with both interaural (representing brainstem level) and dichotic (representing auditory cortex level) protocols.

Results

Complete screening results were obtained from 524 persons. Of these, 401 persons (76%) had a Pass and 123 (24%) a Fail. Ear wax had to be removed in 48% of all 552 athletes. Sixty-five (52.8%) of the Fails were presumably caused by sensorineural problems, 26 (21.1%) by conductive problems, and 32 (26.0%) by a combined hearing loss. There were 87 cases (70.7%) of bilateral, 17 (13.8%) of right-ear, and 19 (15.5%) of assumed left-ear hearing loss. Thirty athletes had a known hearing disorder. There were no significant differences in the frequency of fails (χ2-test) between men and women.

42 percent of the athletes received an advice to consult an otolaryngologist or an acoustician. Among them, 3% needed a consultation because of other ear canal problems, 10% because of middle ear problems, 21% because of a possible sensorineural hearing loss, and 27% needed a regular ear canal control because of blocking ear wax.

Of the 99 athletes whose suspected bilateral (69 cases) or unilateral (30 cases) hearing loss was confirmed by a diagnostic PTA threshold measurement, the bilateral hearing loss was mild (<40 dB) in 31% of the respective cases, moderate (40-69 dB) in 49%, severe (70-94 dB) in 17%, and profound (>95 dB) in 3%. Of the 99 cases with hearing loss, 74% were unknown until then and thus untreated. An alarming 11 of the 14 cases with profound or severe hearing loss were undetected so far. With 195 athletes an additional diagnostic PTA was performed. The correlation between PTA screening and diagnostic PTA yielded a Cramer’s V index of 0.98. The sensitivity of the PTA screening on the basis of these data was 100% (95% confidence interval 98.1% to 100%) and the specificity 98% (95% confidence interval 95.1% to 100%). 20 athletes completed tests of central auditory processing. In the dichotic protocol, all athletes had higher than normal discrimination thresholds for tone duration, 14 for SAM, and 14 for frequency discrimination. During interaural testing, 15 athletes showed an abnormal discrimination threshold for tone duration.

Discussion

The 24% fail rate of the screening described here is comparable with international results of Special Olympics Healthy Hearing screenings [Ref.Â 2]. It indicates the high prevalence of hearing impairment and a high proportion of undetected hearing impairments in this population. The sensitivity and specificity indices of the screening were so satisfactory that the screening alone can be assumed to already deliver a valid diagnosis given good screening conditions. About three-quarters of the bilateral hearing impairments were previously unknown and thus untreated. Pure hearing is already a severe communication handicap for persons with unimpaired cognitive abilities. In intellectually disabled persons, however, poor hearing is even more an obstacle for verbal communication, social orientation, and coping with daily problems. These considerations ought to compel primary care providers of people with intellectual disabilities to arrange regular controls of the hearing status of their fosterlings. The results of the central auditory processing tests reflect a considerable proportion of central auditory processing disorders among persons with intellectual disabilities. Processing disturbances at the cortical level were found in all examined subjects and at the brainstem level in a considerable proportion of them. Frequency processing seemed to be more robust than temporal processing, at least at the brainstem level. In sum, special attention of professionals as well as regular hearing assessment and standard therapy programs are required for persons with intellectual disabilities.